The present invention relates generally to an absorbent composite and, more particularly, to an air-laid composite that includes absorbent material.
Cellulose fibers derived from wood pulp are used in a variety of absorbent articles, for example, diapers, incontinence products, and feminine hygiene products. It is desirable for the absorbent articles to have a high absorbent capacity for liquid, rapid liquid acquisition, low rewet, as well as to have good dry and wet strength characteristics for durability in use and effective fluid management. The absorbent capacity of articles made from cellulose fibers is often enhanced by the addition of absorbent materials, such as superabsorbent polymers. Superabsorbent polymers known in the art have the capability to absorb liquids in quantities from 5 to 100 times or more their weight. Thus, the presence of superabsorbent polymers greatly increases the liquid holding capacity of absorbent articles made from cellulose.
However, absorbent composites that contain superabsorbent materials commonly suffer from gel blocking. Upon liquid absorption, superabsorbent materials tend to coalesce and form a gelatinous mass which prevents the wicking of liquid to unwetted portions of the composite. By preventing distribution of acquired liquid from a composite""s unwetted portions, gel blocking precludes the effective and efficient use of superabsorbent materials in fibrous composites. The wicking capacity of conventional fibrous composites that include relatively homogeneous distributions of superabsorbent material is generally significantly reduced after initial liquid insult. The diminished capacity of such fibrous composites results from narrowing of capillary acquisition and distribution channels that accompanies superabsorbent material swelling. The diminution of absorbent capacity and concomitant loss of capillary distribution channels for conventional absorbent cores that include superabsorbent material is manifested by decreased liquid acquisition rates and far from ideal liquid distribution on successive liquid insults.
Accordingly, there exists a need for an absorbent composite that includes superabsorbent material and that effectively acquires and wicks liquid throughout the composite and distributes the acquired liquid to absorbent material where the liquid is efficiently absorbed and retained without gel blocking. A need also exists for an absorbent composite that continues to acquire and distribute liquid throughout the composite on successive liquid insults. In addition, there exists a need for an absorbent composition containing superabsorbent materials that exhibits the advantages associated with wet-laid composites including wet strength, absorbent capacity and acquisition, liquid distribution, softness, and resilience. The present invention seeks to fulfill these needs and provides further related advantages.
In one aspect, the present invention provides a fibrous absorbent composite that includes absorbent material distributed throughout the composite and in selected regions of the composite. The concentration of absorbent material in these regions can be varied to provide a composite having variable absorbent material concentration. In one embodiment, the composite includes absorbent material dispersed in bands across the composite""s width and that extend along the composite""s length. On contact with liquid, the composite""s bands enriched with absorbent material swell with acquired liquid and expand and rise from the composite""s wetted surface to form ridges and to provide a fluted structure. The wetted composite""s fluted structure enhances liquid wicking, acquisition, and distribution on subsequent liquid insult.
In another aspect of the invention, a method for forming an absorbent composite having variable absorbent material content is provided. In one embodiment, the method includes increasing the concentration of absorbent material in the composite by adding absorbent material to selective regions of the composite. In another embodiment, the method provides for forming regions of increased absorbent material concentration in the composite by selectively increasing the composite""s basis weight. In the method, the composite is formed by selectively densifying a substantially homogeneous composite containing fibers and absorbent material.